A variety of mechanical vibrato systems for guitar have been developed since the 1930s. They are used to add vibrato to the sound by changing the tension of the strings, typically at the bridge or tailpiece of an electric guitar using a controlling lever (often referred to as a whammy bar, vibrato arm/bar, or tremolo arm/bar). The lever enables the player to quickly vary the tension and sometimes the length of the strings temporarily, changing the pitch to create a vibrato or pitch bend effect.
US 2008/0141843 A1 (Thompson) discloses a string bender apparatus that includes a mounting plate with an anchor for anchoring guitar strings to a guitar body, a first section with fastener-receiving holes arranged to receive fasteners extended into pre-existing mounting holes in the body, and an extension that extends from the first section. A lever is pivoted to the extension for movement in a plane that extends generally parallel the front surface of the guitar body. The lever includes a first end defining a handle that is positioned generally adjacent one side of the strings and includes an opposite end attached to one of the strings for temporarily changing a tension of the one string and thus changing a pitch of the one string when the handle is moved in the plane. If desired, the string bender apparatus may include a vibrato. Then, the string bender apparatus is pivotal around its front end and has a second lever for pivoting the rear end of the string bender apparatus upward from the front of the guitar body. The string bender can be retrofit onto existing guitars. The string bender can be made removable and replaced with, or combined with a vibrato. To mount the string bender onto an existing guitar, the anchor or bridge present on the guitar first has to be removed. If possible, the existing holes are used for the mounting of the string bender or else new holes have to be made in the guitar body for screws, bolts or the like, and there is damage to the guitar body.
Another string bender is disclosed in U.S. Pat. No. 5,140,884 (Bowden). Here, the guitar includes a protruding structure such as a bridge or tail piece. The string bender apparatus includes a frame having an actuating lever pivotally attached thereto. The actuating lever is attached to one of the guitar strings for varying the tension on the string by pivoting the actuating lever relative to the frame. An adapter is provided for removably attaching the frame of the string bender apparatus to the protruding structure of the guitar. In the illustrated embodiment, this prior art string bender is mounted on a guitar having a bridge with a top surface in the shape of a roof ridge and spaced therefrom a separate stop bar of generally half-circular cross-section. Each string is laid over the top surface of the bridge and has an enlarged end, which is locked in a passage defined in the tail piece. The string bender is locked to the tail piece by two hollow set screws entering such a passage. The axial bores through the set screws are aligned with the passage through which the guitar string passes through the tail piece to be attached to a grooved rounded end on a rear portion of the pivotal actuating lever.
In another embodiment of the string bender apparatus, the entire apparatus is held in place relative to the guitar by tension in the six guitar strings. Thus, to mount the string bender apparatus onto the guitar, all of the six strings have to be removed and then threaded through the apparatus and the existing openings in the pull-through type bridge and saddle assembly.
The front end of the actuating lever has an inactive end position lifted from the front surface of the guitar body and can be depressed toward the front surface to provide the desired change in pitch. However, to accommodate placement of the guitar in a conventional guitar case, the string bender has to be foldable and thus the frame has to include a fix front part and a rotatable rear part. Such a string bender consists of an unnecessarily large number of parts which makes it expensive and troublesome to mount to a guitar.